The present invention relates to industrial fasteners and more particularly to a plastic resin fastener.
Many types of fasteners have been proposed for use to permit the closing and opening of panels and boxes. Generally it is desired that such fasteners be strong enough to hold the panels together, or retain the cover on a box, under greater forces of separation than are necessary to open or close the fastener. In certain circumstances, for example, on containers used on ships or in chemical plants, it is desirable that the fastener not have any metal parts, i.e., be constructed of a suitable plastic resin to withstand the adverse salt spray or chemical environment. In addition, plastic resin fasteners may be required around sensitive compasses or other types of instruments affected by the presence of metal. In other circumstances a plastic resin fastener may be desirable because of its low weight, its attractive appearance or because of cost factors.
Many of the presently commercially available fasteners, for example, of the type used on tackle or tool boxes, are constructed of metal. Some of those fasteners may use a toggle action in which one or more metal members rotate about a pin. However, if the pin should become damaged or bent because of the opening load or because the container or panel is dropped or mishandled because of rust, the fastener may become inoperative.
U.S. Pat. Nos. 3,181,905 and 3,466,076, both entitled "Draw Pull Catch", show plastic industrial fasteners in which a catch includes, as one of its members, a complex molded member of the plastic resin polypropylene to provide spring-like connecting webs. Such fasteners may be considered to be relatively weak in their web areas and require almost a rotation of the movable member, about 180.degree., before they come into a position to be locked.
U.S. Pat. No. 3,338,449 for "Box Construction" and U.S. Pat. No. 3,109,675 for "Toggle Type Window Lock" each show metal fasteners which operate by a toggle action. Such metal toggle fasteners are not usable in certain applications, for example, in adverse environments such as salt water or chemical spray, or where the metal would interfere with instruments. In addition, the toggle action depends upon a free rotational movement on pins, and the openings for such pins may prove a weak point of the fastener.
A plastic toggle action fastener is shown in U.S. Pat. No. 3,134,617. However, it is relatively complex and may not be able to withstand strong opening forces because it relies upon a relatively thin plastic section.